1. Field of the Invention
The present invention relates to a method of forming a capacitor of a semiconductor device, and more particularly to a method of forming a capacitor of a semiconductor device which can improve an electrical characteristic of a semiconductor device and the reliability dependent upon improving an electrical characteristic of a capacitor by using a dielectric film as dielectric of the capacitor which a step coverage is excellent.
2. Description of the Prior Art
Currently, it is difficult to form a capacitor having enough capacitance because the size of cells are decreased due to the trend in of a high integrated of a semiconductor device.
In particular, in a DPAM device composed of a MOS transistor and a capacitor, a material with a high dielectric constant is used as a dielectric film, or the thickness of a dielectric film is thin, or the surface area of a charge storage electrode is enlarged for increasing the capacitance of a capacitor.
In this regard, although not shown in the drawings, a method of manufacturing a capacitor of a semiconductor device according to the conventional method will be explained as follows.
First, after a device isolation oxide film and a gate oxide film are formed on a semiconductor substrate, MOS field effect transistor composed of a gate electrode and source/drain electrode is formed, and an interlayer insulating film is formed on the entire surface of the structure.
Next, a charge storage electrode contact hole is formed by removing the interlayer insulating film of the top portion prearranged in the charge storage electrode contact of the source/drain electrode, the charge storage electrode contacted with the source/drain electrode through the contact hole is formed into a polycrystal silicon layer pattern.
Subsequently, the dielectric film composed of an oxide film or nitride film or a laminating layer structure of oxide film-nitride film-oxide film on the surface of the charge storage electrode is spread, a capacitor is completed by forming a plate electrode wrapping the charge storage electrode on the dielectric film.
Required are, a specific dielectric constant, a low leakage current density, a high insulating destructive voltage, and a stable interfacial characteristic with the upper and lower electrode for the dielectric film in the capacitor of the semiconductor device according to the prior art such as described above.
The dielectric constant of the oxide film is about 3.8, that of the nitride film is about 7.2, the polycrystal silicon layer used as an electrode limits the capacitance because non-resistance is high to the extent of 800.sup..about. 1000 .mu..OMEGA. cm.
Recently, to solve these problems, a specific dielectric film such as a Ta.sub.2 O.sub.5 film is used instead of the dielectric film composed of the laminating structure of oxide film-nitride film-oxide film.
The use of Ta.sub.2 O.sub.5 film as the dielectric film of the capacitor of a high integrated memory device has been extensively considered. However, using Ta.sub.2 O.sub.5 film as the dielectric film greatly varies the electric characteristic of the capacitor according to the method of depositing the Ta.sub.2 O.sub.5 film.
That is, in case of forming a plat capacitor upon depositing the Ta.sub.2 O.sub.5 film by a plasma enhanced chemical vapor deposition (hereinafter, called PECVD) method, the electrical characteristic is better than depositing the Ta.sub.2 O.sub.5 film by a low pressure chemical vapor deposition(hereinafter, called LPCVD) method.
However, the capacitor used in practice is a device of various structures such as cylinder type and pin structure. In addition, it is necessary that the stepcoverage of the Ta.sub.2 O.sub.5 film be excellent because the step difference of these devices is large.
Furthermore, it is problematic that the high leakage current is caused in case of applying the practical device since the stepcoverage of the Ta.sub.2 O.sub.5 film deposited by the PECVD method is very poor, compared to that of the Ta.sub.2 O.sub.5 film deposited by the LPCVD method.